Free Tools/Webhook Helper

Webhook Helper

Generate a test webhook URL, inspect payload format and build signature verification code.

What is a Webhook?

A webhook is an HTTP callback — a POST request sent to a URL when an event occurs. Instead of polling an API repeatedly, the external service pushes data to your endpoint automatically.

Webhook vs Polling

Polling: Your app asks "anything new?" every N seconds. Webhooks: The service tells you "something happened" in real time. Webhooks are more efficient and faster.

Security

Always verify webhook signatures. Most providers include an HMAC-SHA256 signature in a header (e.g. X-Hub-Signature-256 for GitHub, Stripe-Signature for Stripe). Reject requests with invalid signatures.

Idempotency

Webhooks can be delivered more than once. Use the event ID to detect duplicates and ensure your handler produces the same result when called multiple times.

Response Requirements

Return HTTP 200 within 5–30 seconds (varies by provider). If you need more time, acknowledge immediately then process asynchronously via a job queue.

Provider Comparison

Provider	Signature Header	Algorithm	Event Field	Retries
GitHub	X-Hub-Signature-256	HMAC-SHA256	X-GitHub-Event	Yes (3 attempts)
Stripe	Stripe-Signature	HMAC-SHA256	type (in body)	Yes (72h window)
Slack	X-Slack-Signature	HMAC-SHA256	type (in body)	No
Shopify	X-Shopify-Hmac-Sha256	HMAC-SHA256	X-Shopify-Topic	Yes (19 attempts)
PayPal	PAYPAL-TRANSMISSION-SIG	RSA-SHA256	event_type (body)	Yes

Signature Verification Example

const crypto = require('crypto');

function verifyWebhook(payload, signature, secret) {
  const expected = crypto
    .createHmac('sha256', secret)
    .update(payload, 'utf8')
    .digest('hex');
  
  const sig = signature.replace('sha256=', '');


  return crypto.timingSafeEqual(
    Buffer.from(expected),
    Buffer.from(sig, 'hex')
  );
}

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Built for developers

Encoders, formatters, validators and generators that run entirely in your browser. Whatever you paste stays on your machine — nothing is sent to a server.

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